CIF-Value to Component Carrier Mapping Reconfiguration

ABSTRACT

A radio network node in a multi-carrier radio communication system reconfigures mappings of Carrier Indicator Field values (CIF-values) to component carriers. Each CIF-value is mapped to a respective component carrier comprising a respective shared data channel and a downlink control channel that addresses the shared data channel. The reconfiguring comprises maintaining a first mapping between a first CIF-value and a first component carrier. The downlink control channel of the first component carrier carries the first CIF-value and a second CIF-value. The reconfiguring further comprises changing a second mapping of the second CIF-value to a second component carrier. The radio network node sends the changed second mapping to a user equipment (UE) comprised in the multi-carrier radio communication system. The UE receives the reconfigured mappings and reconfigures the UE to use the mappings for communication in the multi-carrier radio communication system.

RELATED APPLICATION

The present application is a continuation of U.S. patent applicationSer. No. 14/806,054, filed on Jul. 22, 2015, which is a continuation ofU.S. patent application Ser. No. 12/886,031, filed on Sep. 20, 2010, andissued as U.S. Pat. No. 9,124,412 on Sep. 1, 2015, which claims benefitof U.S. Provisional Application No. 61/286,138, filed on Dec. 14, 2009,the disclosures of each of which are herein incorporated by reference intheir entireties.

TECHNICAL FIELD

The present disclosure relates to a method and an arrangement in amulti-carrier radio communication system. In particular, the presentdisclosure relates to a method and an arrangement in a radio networknode for reconfiguring mappings from Carrier Indicator Field-values tocomponent carriers.

BACKGROUND

LTE (Long Term Evolution) uses OFDM (Orthogonal Frequency DivisionMultiplexing) in the downlink and DFT-spread OFDM (Discrete FourierTransform spread Orthogonal Frequency Division Multiplexing) in theuplink. The basic LTE downlink physical resource can thus be seen as atime-frequency grid as illustrated in FIG. 1, where each resourceelement corresponds to one OFDM subcarrier during one OFDM symbolinterval.

In the time domain, LTE downlink transmissions are organized into radioframes of 10 ms, each radio frame consisting of ten equally-sizedsubframes of length Tsubframe=1 ms as seen in FIG. 2.

Furthermore, the resource allocation in LTE is typically described interms of resource blocks, where a resource block corresponds to one slot(0.5 ms) in the time domain and 12 contiguous subcarriers in thefrequency domain. Resource blocks are numbered in the frequency domain,starting with 0 from one end of the system bandwidth.

Downlink transmissions are dynamically scheduled, in that in eachsubframe (or transmission time interval, TTI) the base station transmitscontrol information about to which terminals data is transmitted andupon which resource blocks the data is transmitted, in the currentdownlink subframe. This control signaling is typically transmitted inthe first 1, 2, 3 or 4 OFDM symbols in each subframe. A downlink systemwith 3 OFDM symbols as control is illustrated in FIG. 3.

To transmit data in the uplink the mobile terminal has to have beenfirst assigned an uplink resource for data transmission, on the PhysicalUplink Shared Channel (PUSCH). In contrast to a data assignment indownlink, in uplink the assignment of resource blocks must always beconsecutive in frequency, to retain the single carrier property of theuplink as illustrated in FIG. 4.

The LTE Rel-8 standard has recently been standardized, supportingbandwidths up to 20 MHz. However, in order to meet the upcomingIMT-Advanced requirements, 3GPP has initiated work on LTE-Advanced. Oneof the parts of LTE-Advanced is to support bandwidths larger than 20MHz. One important requirement on LTE-Advanced is to assure backwardcompatibility with LTE Rel-8. This should also include spectrumcompatibility. That would imply that an LTE-Advanced carrier, wider than20 MHz, should appear as a number of LTE carriers to an LTE Rel-8terminal. Each such carrier can be referred to as a component carrier(CC). In particular for early LTE-Advanced deployments it can beexpected that there will be a smaller number of LTE-Advanced-capableterminals compared to many LTE legacy terminals. Therefore, it isnecessary to assure an efficient use of a wide carrier also for legacyterminals, i.e., that it is possible to implement carriers where legacyterminals can be scheduled in all parts of the wideband LTE-Advancedcarrier. The straightforward way to obtain this would be by means ofcarrier aggregation. Carrier aggregation implies that an LTE-Advancedterminal can receive multiple component carriers, where the componentcarriers have, or at least the possibility to have, the same structureas a Rel-8 carrier. Carrier aggregation is illustrated in FIG. 5.

The number of aggregated component carriers as well as the bandwidth ofthe individual component carrier may be different for uplink anddownlink. A symmetric configuration refers to the case where the numberof component carriers in downlink and uplink is the same, whereas anasymmetric configuration refers to the case that the number of componentcarriers is different. It is important to note that the number ofcomponent carriers configured in a cell may be different from the numberof component carriers seen by a terminal: A terminal may, for example,support more downlink component carriers than uplink component carriers,even though the cell is configured with the same number of uplink anddownlink component carriers.

Scheduling of the component carriers is done on the Physical DownlinkControl Channel (PDCCH) via downlink assignments. Uplink grants are alsosignaled via PDCCH. Control information on the PDCCH is formatted as aDownlink Control Information (DCI) message. DCI messages for downlinkassignments contain among others resource block assignment, modulationand coding scheme related parameters, hybrid-ARQ redundancy version,etc. In addition to those parameters that relate to the actual downlinktransmission most DCI formats for downlink assignments also contain abit field for Transmit Power Control (TPC) commands. These TPC commandsare used to control the uplink power control behavior of thecorresponding PUCCH that is used to transmit the hybrid-ARQ feedback.

The design of PDCCH in LTE Rel-10 follows very much that one in Rel-8/9.Assignments and grants of each component carrier are separately encodedand transmitted within a separate PDCCH. Main motivation for choosingseparately encoded PDCCH over a jointly encoded PDCCH—here DCI messagesfrom multiple component carriers would be lumped together into oneentity, jointly encoded and transmitted in a single PDCCH—wassimplicity.

In LTE Rel-10, the PDCCH is extended to include a Carrier IndicatorField (CIF), which is not present in LTE Rel-8/9. The CIF may consist ofthree bits attached to the DCI message which points to that componentcarrier the corresponding shared channel is located at. For a downlinkassignment the CIF points to the component carrier carrying the PDSCHwhereas for an uplink grant the three bits are used to address thecomponent carrier conveying Physical Uplink Shared Channel (PUSCH). Forsimplicity this field is always three bits.

If CIF is configured, every downlink assignment and uplink grantcontains the CIF bits, even if the assignment addresses PDSCH within thecomponent carrier (or PUSCH within the linked uplink component carrierfor uplink grants). With no CIF configured, the carrier aggregationlooks like multiple parallel Rel-8/9 carriers, see FIG. 7. FIG. 8 showsthe relation between PDCCH and PDSCH with configured CIF. A terminalconfigured with more uplink component carriers than downlink componentcarriers always requires an uplink grant with CIF.

The mapping of the CIF to component carriers could be done according toone of two different possibilities:

-   -   cell-specific mapping, i.e., the same mapping from CIF value to        component carrier number is used by all user equipments (UEs) in        the cell. The mapping could either be given according to rules        or tables in the upcoming Rel-10 specifications or be signaled        as part of the system information in the cell. With a        cell-specific approach, the mapping is expected to be fixed or        changed very infrequently.    -   UE-specific mapping, i.e. each user equipment (UE) has its own        mapping from CIF to component carrier number. In this case, the        CIF-to-component-carrier mapping is signaled as part of the        UE-specific configuration information. Changing the mapping can,        in this alternative, be more frequent than in the cell-specific        alternative.

Over time the user equipment will have the possibility to receive ortransmit data on different component carriers, but not necessarily onall component carriers that a radio network node, such as an eNB,transmits in its cell(s). If the user equipment were required to receiveall component carriers transmitted by the radio network node, this wouldresult in short battery time and more memory consumption, for example.Furthermore, the radio network node has also the possibility to turn offcomponent carriers, e.g., to enable power saving.

If UE-specific CIF-to-CC mapping is used, a problem will occur when themapping from CIF-values to component carriers is updated. Duringupdating of the mapping, the radio network node sends the reconfiguredmappings to the user equipment and the network cannot communicate withthe user equipment. This may lead to lost calls and degradedperformance.

SUMMARY

An object may be to improve performance of connection to user equipmentsduring updating of mapping from CIF-values to component carrier.

According to an aspect, the object is achieved by a method in a radionetwork node for reconfiguring mappings from Carrier IndicatorField-values, referred to as “CIF-values”, to component carriers. EachCIF-value is mapped to a respective component carrier comprising arespective shared data channel. Each respective shared data channelcorresponds to at least one downlink control channel carrying said eachCIF-value. The component carriers are managed by the radio network node.The radio network node and the user equipment are comprised in amulti-carrier radio communication system. In an initial step, the radionetwork node reconfigures mappings from CIF-values to componentcarriers, while at least one mapping of CIF-value to component carrieris maintained. The component carrier of said at least one mapping fromCIF-value to component carrier comprises said at least one downlinkcontrol channel and a shared data channel corresponding to said at leastone downlink control channel. Further, the radio network node sends atleast one of the reconfigured mappings from CIF-values to componentcarriers to the user equipment.

According to another aspect, the object is achieved by an arrangement ina radio network node for reconfiguring mappings from Carrier IndicatorField-values to component carriers. Each CIF-value is mapped to arespective component carrier comprising a respective shared datachannel. Each respective shared data channel corresponds to at least onedownlink control channel carrying said each CIF-value. The componentcarriers are managed by the radio network node. The radio network nodeand the user equipment are comprised in a multi-carrier radiocommunication system. The arrangement may comprise a reconfiguringcircuit configured to reconfigure mappings from CIF-values to componentcarriers, while at least one mapping of CIF-value to component carrieris maintained. The component carrier of said at least one mapping fromCIF-value to component carrier comprises said at least one downlinkcontrol channel and a shared data channel corresponding to said at leastone downlink control channel. The arrangement may further comprise atransceiver configured to send at least one of the reconfigured mappingsfrom CIF-values to component carriers to the user equipment.

Thanks to the fact that the mapping of CIF-value to component carrier issent to the user equipment while at least one mapping of CIF-value tocomponent carrier is maintained, the user equipment may continue totransmit on the component carrier corresponding to said at least onemapping of CIF-value to component carrier. As a result, improvedperformance of connection to the user equipment during updating ofmapping from CIF-value to component carrier is achieved.

Expressed differently, mapping of one CIF-value to one component carrieris fixed, i.e., not changed during reconfiguration (or determination) ofthe CIF-CC-mapping. In this manner, there will be a component carrieravailable for transmission even during updating of the mapping fromCIF-value to component carrier. As a result, a user equipment maytransmit/receive continuously by use of the component carrier associatedto the CIF-value whose interpretation is kept even though theCIF-CC-mapping is updated for other CIF-values.

An advantage is that the number of lost calls/connections duringupdating of the CIF-CC-mapping in the user equipment may be reduced.Moreover, degraded connection performance due to updating of mappingfrom CIF-values to component carriers may be avoided.

Further features of, and advantages with, embodiments of the presentinvention will become apparent when studying the appended claims and thefollowing description. It is to be understood that different features ofembodiments according to the present invention may be combined to createembodiments other than those described in the following, withoutdeparting from the scope of the present invention, which is defined bythe appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The various aspects of the embodiments disclosed herein, including itsparticular features and advantages, will be readily understood from thefollowing detailed description and the accompanying drawings, in which:

FIG. 1 illustrates schematically an LTE downlink physical resource;

FIG. 2 illustrates schematically an LTE time-domain structure;

FIG. 3 illustrates schematically a Downlink subframe;

FIG. 4 illustrates schematically a PUSCH resource assignment;

FIG. 5 illustrates carrier aggregation,

FIG. 6 shows a schematic overview of an exemplifying radio communicationsystem in which the present solution may be implemented,

FIG. 7 shows five exemplifying component carriers, in which no CIF isconfigured in the DCI message of the downlink control channel,

FIG. 8 shows three exemplifying component carriers, in which CIF2 ismapped to component carrier f3,

FIG. 9 shows two exemplifying component carriers, in which CIF2 ismapped to component carrier f1,

FIG. 10 shows a schematic, combined signalling and flow chart of anembodiment of a method in the radio communication system according toFIG. 6 for reconfiguring mappings from Carrier Indicator Field-values tocomponent carriers,

FIG. 11 shows a schematic flow chart of an embodiment of the method inthe radio network node for reconfiguring mappings from Carrier IndicatorField-values to component carriers, and

FIG. 12 shows a schematic block diagram of an embodiment of thearrangement in the radio network node.

DETAILED DESCRIPTION

Throughout the following description similar reference numerals havebeen used to denote similar elements, parts, nodes, systems, items orfeatures, when applicable.

In FIGS. 7, 8 and 9, there are shown different examples of componentcarriers with CIF enabled and with CIF disabled. In FIG. 7, the CIF isdisabled, whereas in FIGS. 8 and 9, the CIF is enabled. Moreover, FIG. 8shows a configuration, where the CIF-value to component carrier mappingis different from the CIF-value to component carrier mapping shown bythe configuration depicted in FIG. 9.

FIG. 6 shows a schematic overview of an exemplifying multi-carrier radiocommunication system 100, in which embodiments may be implemented. Themulti-carrier radio communication system 100 comprises a radio networknode 130 and a user equipment 120. The arrow indicates that the userequipment 120 may exchange information with the radio network node 130using, for example, a downlink control channel such as PDCCH, and ashared data channel such as PDSCH or PUSCH.

FIG. 7 shows five exemplifying component carriers f1, f2, f3, f4, f5, inwhich no CIF is configured in the DCI message of the downlink controlchannel. As shown in FIG. 5, an radio communication system, such asLTE-Advance, may use an aggregated carrier, comprising five componentcarrier of 20 MHz each. In FIG. 7, it may be seen that each componentcarrier has its own separately encoded PDCCH. In the enlarged view ofthe PDCCH, it is shown that the Downlink Control Information (DCI)message does not include a CIF-value. Since no CIF is used, PDCCH pointsto PDSCH allocated on the same component carrier as indicated by thearrows.

FIG. 8 shows three exemplifying component carriers f1, f2, f3, in whichCIF2 is mapped to component carrier f3. In FIG. 8, the DCI message, asshown by the enlarged view, comprises a CIF-value. Hence, CIF isenabled. Downlink assignments transmitted in one component carrier maypoint to PDSCH within another component carrier. In this case, theCIF-value of PDCCH of component carrier f2 cross-schedules to a PDSCH ofa component carrier f3. See arrows between component carrier f2 andcomponent carrier f3.

It may be noted that mapping from CIF-value to component carrier may berealized in the form of a table or matrix, where for example a rowcomprising one CIF-value and one component carrier indicates that thisparticular CIF-value is mapped to the component carrier on that row.Hence, one or more pairs, wherein each pair comprises one CIF-value andone corresponding component carrier, are formed to express the mappingfrom CIF-values to component carriers. Thus, one mapping refers to onesuch pair comprising a CIF-value and a component carrier (or rathercomponent carrier number for indicating a component carrier).

In FIG. 9, the CIF-values of the situation in FIG. 8 have beenreconfigured. The radio network node 130 has also decided to switch off(shut down) component carrier f3. Now CIF-value CIF2 is mapped to acomponent carrier f1 as indicated by the arrows. In FIG. 8, CIF-valueCIF2 was mapped to component carrier f3. Notably, CIF-value CIF1 iskept, i.e. points to component carrier f2 in both FIGS. 8 and 9, suchthat this CIF-value and the respective component carrier f2 may be usedby the user equipment 120 during updating of mappings from CIF-value tocomponent carrier.

In FIG. 10, there is shown a schematic, combined signalling and flowchart of an embodiment of a method in the radio communication system 100according to FIG. 6 for reconfiguring mappings from Carrier IndicatorField-values to component carriers.

Each CIF-value is mapped to a respective component carrier comprising arespective shared data channel. Each respective shared data channelcorresponds to at least one downlink control channel carrying (orcomprising) said each CIF-value. The component carriers are managed bythe radio network node 130. The radio network node 130 and the userequipment 120 are comprised in a multi-carrier radio communicationsystem 100. The following steps may be performed. Notably, in someembodiments of the method the order of the steps may differ from what isindicated below.

210: The radio network node 130 reconfigures mappings from CIF-values tocomponent carriers, while maintaining at least one mapping of CIF-valueto component carrier. The component carrier of said at least one mappingfrom CIF-value to component carrier comprises said at least one downlinkcontrol channel and a shared data channel corresponding to said at leastone downlink control channel.

220: The user equipment 120 receives at least one of the reconfiguredmappings from CIF-values to component carriers from radio network node130.

The present solution enables the radio network node 130, such as an eNB,to always have the possibility to schedule data on the component carrierthat carries PDCCH and PDSCH (or the anchor carrier, also referred to asprimary cell). Hence, the radio network node 130 may schedule the userequipment even when it is reconfiguring all its other CIF-to-componentcarrier mappings. In some embodiments, this also enables lower signalingoverhead on the Radio Resource Control protocol and avoids drop ofcommunication between the user equipment 120 and the radio network node130 during updating of mapping. In a scenario where the user equipmenthas initiated hand-over directly before updating of mapping, the userequipment may need to transmit with high power in order to keepconnection. In such a scenario, embodiments avoid extensive userequipment battery consumption and/or unnecessary user equipment memoryusage.

FIG. 11 illustrates an exemplifying method in a radio network node 130for reconfiguring mappings from Carrier Indicator Field-values tocomponent carriers. The flow chart of FIG. 11 corresponds to thecombined signalling and flow chart of FIG. 10. Where applicable the samereference numerals have been used. Each CIF-value is mapped to arespective component carrier comprising a respective shared datachannel. Each respective shared data channel corresponds to at least onedownlink control channel carrying (or comprising) said each CIF-value.The component carriers are managed by the radio network node 130. Theradio network node 130 and the user equipment 120 are comprised in amulti-carrier radio communication system 100. The following steps may beperformed. Notably, in some embodiments of the method the order of thesteps may differ from what is indicated below.

210: The radio network node 130 reconfigures mappings from CIF-values tocomponent carriers, while maintaining at least one mapping of CIF-valueto component carrier. The component carrier of said at least one mappingfrom CIF-value to component carrier comprises said at least one downlinkcontrol channel and a shared data channel corresponding to said at leastone downlink control channel.

220: The radio network node 130 sends at least one of the reconfiguredmappings from CIF-values to component carriers to the user equipment120.

In some embodiments of the method in the network node 130, wherein thecomponent carrier of said at least one mapping from CIF-value tocomponent carrier corresponds to a primary cell, wherein the primarycell is one of the component carriers managed by the radio network node130. An advantage may be that, from a user equipment perspective,channel quality may be better on the primary cell as compared to othercells.

In some embodiments of the method in the network node 130, the CIF-valueof said at least one mapping from CIF-value to component carrier isequal to zero.

In some embodiments of the method in the network node 130, the sending230 of the configured mapping further comprises refraining 230 fromsending said at least one mapping from CIF-value to component carrier tothe user equipment 120. As a consequence, said at least one mapping fromCIF-value to component carrier may need to be predetermined. Anadvantage may be that less information needs to be sent from the radionetwork node 130 to the user equipment 120.

In some embodiments of the method in the network node 130, the controlchannel is PDCCH and the shared data channel is PDSCH or PUSCH in casethe multi-carrier radio communication system is an LTE system. Hence, itmay be noted that embodiments presented herein may be applicable to bothdownlink assignments and uplink grants.

In some embodiments of the method in the network node 130, the step ofsending at least some of the reconfigured mappings is performed usingRadio Resource Control protocol, sometimes referred to as RRC-protocol.

Now referring to FIG. 12, there is illustrated an arrangement 400 in theradio network node 130 configured to perform the method described above.The arrangement 400 is, hence, configured to reconfigure mappings fromCarrier Indicator Field-values to component carriers. Each CIF-value ismapped to a respective component carrier comprising a respective shareddata channel. Each respective shared data channel corresponds to atleast one downlink control channel carrying said each CIF-value. Thecomponent carriers are managed by the radio network node 130. The radionetwork node 130 and the user equipment 120 are comprised in amulti-carrier radio communication system 100. The arrangement 400 maycomprise a reconfiguring circuit 410 configured to reconfigure mappingsfrom CIF-values to component carriers, while maintaining at least onemapping of CIF-value to component carrier. The reconfiguring circuit 410may be a processing circuit/unit, a processor, an application specificintegrated circuit (ASIC), a field-programmable gate array (FPGA) or thelike. The component carrier of said at least one mapping from CIF-valueto component carrier comprises said at least one downlink controlchannel and a shared data channel corresponding to said at least onedownlink control channel. The arrangement 400 further comprises atransceiver 420 configured to send at least one of the reconfiguredmappings from CIF-values to component carriers to the user equipment120. Moreover, the arrangement 400 may comprise a memory 430 for storingsoftware to be executed by, for example, the processor. The software maycomprise instructions to enable the processor to perform the methoddescribed above.

In some embodiments of the arrangement 400 in the radio network node130, the transceiver 420 may be a sending/receiving unit or may comprisea transmitter and/or a receiver as appropriate.

In some embodiment of the arrangement 400 in the radio network node 130,wherein the component carrier of said at least one mapping fromCIF-value to component carrier corresponds to a primary cell, whereinthe primary cell is one of the component carriers managed by the radionetwork node 130. An advantage may be that, from a user equipmentperspective, channel quality may be better on the primary cell ascompared to other cells.

In some embodiment of the arrangement 400 in the radio network node 130,the CIF-value of said at least one mapping from CIF-value to componentcarrier is equal to zero.

In some embodiment of the arrangement 400 in the radio network node 130,the transceiver 420 further is configured to refrain from sending saidat least one mapping from CIF-value to component carrier to the userequipment 120. As a consequence, said at least one mapping fromCIF-value to component carrier may need to be predetermined. Anadvantage may be that less information needs to be sent from the radionetwork node 130 to the user equipment 120.

In some embodiment of the arrangement 400 in the radio network node 130,the control channel is PDCCH and the shared data channel is PDSCH orPUSCH

In some embodiment of the arrangement 400 in the radio network node 130,the transceiver 420 may further be configured to use Radio ResourceControl protocol when sending at least some of the reconfigured mappingsto the user equipment 120.

According to some embodiments, the mapping of one of the CIF valuesshould be fixed, so that is not possible to reconfigure the componentcarrier that carries both the PDCCH and PDSCH (e.g. component carrier f2in FIGS. 8 and 9).

In an example of an embodiment, the interpretation of one CIF value isfixed by the specification, i.e. not reconfigurable, to point to thesame component carrier that the PDCCH is transmitted upon. The fixed CIFvalue may be either defined by the standard, e.g. always CIF=0, or maybe configured to the same value for all UEs through RRC signaling(broadcast or dedicated signaling). In one example this componentcarrier would correspond to a value of CIF=0. Hence, even during thereconfiguration period, one CIF value may be used without ambiguity andhence there is always a possibility for the network to communicate withthe terminal.

In an example of an embodiment, the interpretation of one CIF value isfixed to point to a predefined component carrier, e.g. the so-calledanchor carrier. The anchor carrier is a component carrier which the UEalways has to monitor (subject to any Discontinuous Transmission cycle,abbreviated as DTX cycle), e.g. for receiving system information. Theanchor carrier may also be referred to as the primary cell according to3GPP-terminology.

Even though a number of embodiments of the present invention have beendescribed, many different alterations, modifications and the like willbecome apparent for those skilled in the art. The described embodimentsare therefore not intended to limit the scope of the invention, which isdefined by the appended claims.

What is claimed is:
 1. A method, implemented by a radio network node in a multi-carrier radio communication system, the method comprising: reconfiguring mappings of Carrier Indicator Field values (CIF-values) to component carriers, each CIF-value being mapped to a respective component carrier comprising a respective shared data channel and a downlink control channel that addresses the shared data channel, the reconfiguring comprising: maintaining a first mapping between a first CIF-value and a first component carrier, the downlink control channel of the first component carrier carrying the first CIF-value and a second CIF-value; and changing a second mapping of the second CIF-value to a second component carrier; sending the changed second mapping to a user equipment comprised in the multi-carrier radio communication system.
 2. The method of claim 1, wherein the first component carrier corresponds to a primary cell and is managed by the radio network node.
 3. The method of claim 1, wherein the first CIF-value is equal to zero.
 4. The method of claim 1, wherein sending the changed second mapping comprises refraining from sending the maintained first mapping to the user equipment.
 5. The method of claim 1, wherein the downlink control channel of the first component carrier is a Physical Downlink Control Channel and the shared data channel of the first component carrier is a Physical Downlink Shared Channel or a Physical Uplink Shared Channel.
 6. The method of claim 1, wherein the sending of the changed second mapping is performed using Radio Resource Control protocol.
 7. An arrangement comprised in a radio network node configured to operate in a multi-carrier radio communication system, the arrangement comprising: processing circuitry configured to reconfigure mappings of Carrier Indicator Field values (CIF-values) to component carriers, each CIF-value being mapped to a respective component carrier comprising a respective shared data channel and a downlink control channel that addresses the shared data channel, wherein to reconfigure the mapping, the processing circuitry is configured to: maintain a first mapping between a first CIF-value and a first component carrier, the downlink control channel of the first component carrier carrying the first CIF-value and a second CIF-value; and change a second mapping of the second CIF-value to a second component carrier; a transceiver communicatively coupled to the processing circuitry and configured to send the changed second mapping to a user equipment comprised in the multi-carrier radio communication system.
 8. The arrangement of claim 7, wherein the first component carrier corresponds to a primary cell managed by the radio network node.
 9. The arrangement of claim 7, wherein the first CIF-value is equal to zero.
 10. The arrangement of claim 7, wherein to send the changed second mapping, the transceiver is configured to refrain from sending the maintained first mapping to the user equipment.
 11. The arrangement of claim 7, wherein the downlink control channel of the first component carrier is a Physical Downlink Control Channel and the shared data channel of the first component carrier is a Physical Downlink Shared Channel or a Physical Uplink Shared Channel.
 12. The arrangement of claim 7, wherein to send the changed second mapping, the transceiver is configured to use Radio Resource Control protocol.
 13. A method, implemented in a User Equipment (UE) in a multi-carrier radio communication system, the method comprising: receiving mappings of Carrier Indicator Field values (CIF-values) to component carriers, each CIF-value being mapped to a respective component carrier comprising a respective shared data channel and a downlink control channel that addresses the shared data channel, the mappings having been reconfigured by a radio network node in the multi-carrier radio communication system such that: a first mapping between a first CIF-value and a first component carrier is maintained, the downlink control channel of the first component carrier carrying the first CIF-value and a second CIF-value; and a second mapping of the second CIF-value is changed to a second component carrier; reconfiguring the UE to use the reconfigured mappings for communication in the multi-carrier radio communication system.
 14. The method of claim 13, wherein the first CIF-value corresponds to a primary cell managed by the radio network node.
 15. The method of claim 13, wherein the first CIF-value is equal to zero.
 16. The method of claim 13, wherein the downlink control channel of the first component carrier is a Physical Downlink Control Channel and the shared data channel of the first component carrier is a Physical Downlink Shared Channel or a Physical Uplink Shared Channel.
 17. The method of claim 13, wherein receiving the reconfigured mapping is performed using Radio Resource Control protocol.
 18. A User Equipment (UE) configured to operate in a multi-carrier radio communication system, the UE comprising: receiver circuitry configured to receive mappings of Carrier Indicator Field values (CIF-values) to component carriers, each CIF-value being mapped to a respective component carrier comprising a respective shared data channel and a downlink control channel that addresses the shared data channel, the mappings having been reconfigured by a radio network node in the multi-carrier radio communication system such that: a first mapping between a first CIF-value and a first component carrier is maintained, the downlink control channel of the first component carrier carrying the first CIF-value and a second CIF-value; and a second mapping of the second CIF-value is changed to a second component carrier; processing circuitry communicatively coupled to the receiver circuitry and configured to reconfiguring the UE to use the reconfigured mappings for communication in the multi-radio communication system.
 19. The UE of claim 18, wherein the first CIF-value corresponds to a primary cell managed by the radio network node.
 20. The UE of claim 18, wherein the first CIF-value is equal to zero.
 21. The UE of claim 18, wherein the downlink control channel of the first component carrier is a Physical Downlink Control Channel and the shared data channel of the first component carrier is a Physical Downlink Shared Channel or a Physical Uplink Shared Channel.
 22. The UE of claim 18, wherein to receive the mappings, the receiver circuitry is configured to use Radio Resource Control protocol. 